In recent years, multilayer wiring structures have been employed to achieve high speed operation and miniaturization of semiconductor devices. However, these structures have raised the problem of wiring delay due to an increase in the overall wiring resistance and parasitic capacitance of the wiring layers.
The use of low resistance wiring material, e.g. copper (Cu), as the interconnection body reduces the wiring resistance. On the other hand, low permittivity or low-k materials may be used to reduce the parasitic capacitance. Specially, fluorine added carbon (fluorocarbon: CFx) may be used as the insulating layer to reduce parasitic capacitance then to improve the operating speed of semiconductor devices.
To prevent copper (Cu) from diffusing into the insulating layer, a barrier layer is provided between the interconnection body and the insulating layer. The barrier layer of the semiconductor devices is made from titanium (Ti), tantalum (Ta), tungsten (W), ruthenium (Ru), or phosphorus (P).
When fluorocarbon (CFx) is used as the material for the insulating layer, the fluorine contained in the CFx layer causes fluorination reaction at the interface between the CFx layer and the barrier layer. As a result, the adhesiveness between the CFx layer and the barrier layer decreases, thereby the adhesiveness between the insulating layer and the interconnection body deteriorates consequently.
On the other hand, the fluorocarbon (CFx) material is required to have sufficient adhesiveness with a barrier layer which is mainly formed from a metal element. Since subsequent processes such as, for example, chemical and mechanical polishing (CMP) process or wire bonding process, are used in the manufacturing of semiconductor devices, further stress are applied onto the substrate. Therefore, the barrier layer may be peeled-off form the insulating layer if the adhesiveness is poor between the barrier layer and the CFx insulating layer.
The present invention is proposed in view of the above aforementioned problems. The present invention provides surface treatment methods to suppress the fluorination reaction at the interface between the insulating layer and the barrier layer. Further, the present invention provides a barrier layer forming method to increase the adhesiveness between the insulting layer and the barrier layer while suppressing the fluorination reaction there between.